1. Field of the Invention
The present invention relates generally to a method for controlling electromechanical valves in an internal combustion engine.
2. Background of the Invention
An electromechanically operated poppet valve in the cylinder head of an internal combustion, as disclosed in U.S. Pat. No. 4,455,543, is actuated by energizing and de-energizing electromagnets acting upon an armature coupled to the poppet valve. Because the actuation of the electromagnets is controlled by an electronic control unit, valve opening and closing events occur independently of engine rotation. In conventional engines with camshaft actuated valves, which have timings based on engine rotation, air delivery to the cylinders is controlled by a throttle valve placed in the inlet duct of the engine. In contrast, electromechanical valves are capable of controlling air delivery based on valve timing, thereby providing a thermal efficiency improvement over throttled operation of a conventional engine.
However, a drawback to electromechanical valves is the amount of electrical energy consumed in actuating them. The inventors of the present invention have recognized a method to operate electromechanical valves in a manner which consumes less electrical energy than prior methods.
Disadvantages of prior methods are overcome by a method for actuating an intake valve disposed in a cylinder head of an internal combustion engine by an electromagnetic valve apparatus. The apparatus has a valve closing electromagnet capable of exhibiting an electromagnetic force for attracting the armature to close the valve, a valve opening electromagnet capable of exhibiting an electromagnetic force for attracting the armature to open the valve, a valve opening spring for biasing the armature in a direction to open the valve, and a valve closing spring for biasing the armature in a direction to close the valve. The method includes the steps of actuating the valve according to a first mode when a first set of engine operating conditions are detected and actuating the valve according to a second mode when a second set of engine operating conditions are detected. The first mode further includes the steps of de-energizing the valve closing electromagnet, maintaining the valve closing electromagnet in the de-energized state for a first predetermined time enabling the valve to oscillate by force of the valve opening spring and the valve closing spring, and energizing the valve closing electromagnet after the first predetermined time to close the valve. The second mode further includes the steps of de-energizing the valve closing electromagnet to allow the valve to open, energizing the valve opening electromagnet in response to said de-energizing step to attract the armature to the valve opening electromagnet thereby causing the valve to open, de-energizing the opening electromagnet after a second predetermined time has elapsed since the valve opening electromagnet has been energized, and energizing the valve closing electromagnet in response to the de-energizing step of the valve opening electromagnet to attract the armature to the valve closing electromagnet thereby causing the valve to close.
An electromagnetic valve apparatus for actuating a valve disposed in a cylinder head of a multi-cylinder internal combustion engine is disclosed which has an armature operatively connected to the valve, a valve closing electromagnet capable of exhibiting an electromagnetic force for attracting said armature to close the valve, a valve opening spring coupled to the armature for biasing the armature in a direction to open the valve, a valve closing spring coupled to the valve for biasing the valve to a closed position, and an electronic control unit operably connected to the valve closing electromagnet. The electronic control unit de-energizes the valve closing electromagnet allowing the valve to oscillate by force of the valve opening spring and the valve closing spring and maintains the valve closing electromagnet in the de-energized state at least until the valve travels to a nearly open position and returns to a nearly closed position. The predetermined time is based on dynamic characteristics of the valve and the electromagnetic valve apparatus. The valve is an intake valve of the engine. Intake air flows past an oscillating intake valve.
A primary advantage of the present invention is that the amount of energy utilized in actuating a valve is approximately half of prior art actuation methods.
According to an aspect of the present invention, the valve may be opened for a period of time over which the valve oscillates between a nearly open position and a nearly closed position. Compared with prior methods in which the valve is maintained in a fully open position for the entire duration of opening, the present invention provides more intake turbulence to the incoming air stream by virtue of the air being inducted past an intake valve which is at a half open position, on average.